The urinary system consists of four components: a pair of kidneys, a pair of ureters leading to the bladder, and a urethra. Urine is made in the kidneys through a process of filtration and reabsorption and tubular secretion via osmosis, or water moving across a semi-permeable membrane, where water/urine is concentrated, travels down a pair of ureters to the bladder, where it is stored until micturition (signal for need for urination), where it exits through the urethra and is expelled from the body.
Cellular metabolism, the sum of all the reactions that occur in the cells of the body, results in quite a few byproducts, or waste products. Many of these products are rich in nitrogen, and undergo a cycle of breakdown (nitrogen cycle) to be cleared from the bloodstream and maintain homeostasis and the health of the individual. This is how and why the body creates urine, to rid the body of these harmful toxins, mainly urea, uric acid, and creatinine. Interestingly, some of these waste products, particularly urea, are also excreted in small amounts in sweat and perspiration.
Inside the kidneys and bladder, urine is typically sterile, meaning it normally contains no microorganisms unless and individual is experiencing an infection. Urine is composed of an average of about 95% water (range of 91-96%) with dissolved waste products. Ammonia, or NH3, is a compound of nitrogen and hydrogen with a characteristic, pungent odor. In fact, it is what contributes the most to the smell of urine. The longer it sits, the stronger urine smells because bacteria also produce ammonia as a waste product. Sometimes this is the first indication of a bladder or urinary tract infection. The skin surrounding the urethra (external) is colonized with bacteria, often facultative anaerobes, Gram-negative bacilli and cocci. This is why urinary catheter insertion presents an opportunity for infection due to the inadvertent entry of these organisms into the bladder.
The water-soluble phosphate, chloride, magnesium, calcium, potassium and sodium are our electrolytes that are charged atoms (ions) that are responsible for creating the electrochemical potential, or electrochemical gradient that drives movement across cell membranes (membrane potential) for muscle movement, nerve impulses and signals, and heartbeat. What is left in the urine are excesses that the body no longer needs. In addition to ammonia, creatinine, uric acid, and urea are waste products as a result of the urea cycle. Urea is one of the components that gives urine its characteristic yellow color. The normal color of urine is the color of straw. Urine also contains unneeded proteins (amino acids) and hormones as well.
Bulk elements found in urine include:
Carbon (6.87 g/Liter)
Oxygen (8.25 g/Liter)
Nitrogen (8.12 g/Liter)
Hydrogen (1.12 g/Liter)
How Much Urine Is Produced Daily?
Average urine production in human adults: approximately 1.4 Liters of urine per day
Average range of urine production in human adults: 0.6-2.6 Liters of urine per day
6-8 urinations per day, average, per person
Factors Affecting Urine Production and Excretion:
Male or female
State of hydration
Too little = dehydration
Too much
Activity level
Sports
Exercise
Travel
Sedentary lifestyle
Type of foods/beverages taken in
High sodium = water retention/bloating
Medications
Diuretics: medications given to lower the blood pressure but they increase urine output
Environmental Factors
Climate/weather (increased heat = decreased urine output if you are not drinking enough water; increased heat = increased sweat/perspiration)
Weight
Individual's health
Illnesses will affect (Diabetes insipidus, Diabetes mellitus types 1 and 2, Kidney diseases, Infections, High blood pressure, Etc...)
Polyuria:
Excessive urine production (>2.6 Liters/day/adults)
Oliguria:
Too little urine production (<400 mL/day/adults)
Anuria:
Little to no urine production (<100 mL/day/adults)
Nocturia:
Waking up >1x per night to urinate/adults
The components of urine
A normal, straw-colored urine sample
Image courtesy:By en:User:Markhamilton (English Wikipedia, User:Markhamilton) [Public domain], via Wikimedia Commons
This is a normal sample of urine, with a normal, pale yellow color
The normal color of urine is colorless to pale yellow to straw colored, as seen in these three examples above. The yellowish color is due to the presence of urobilin, a byproduct from the breakdown of the "heme" portion of hemoglobin when red blood cells have died. Red blood cells contain the pigment hemoglobin, a 4-dimensional protein that carries oxygen throughout the body. The "heme" portion contains iron, which binds oxygen and carries it throughout the bloodstream to the tissues of the body. Red blood cells only live about 120 days, at which point they cycle through the spleen and the shell is destroyed, but the parts of hemoglobin are broken down. "Heme" ends up in the urine as urobilin, and the global chains are recycled in the building of new red blood cells in the bone marrow.
This chart shows the colors of normal urine versus the color of urine from a person who is dehydrated and needs to drink more water
Colorless urine may be normal, may signify over-hydration, but if chronic, can signify an underlying illness such as Diabetes insipidus. In a drug test, colorless urine may simply be water in an attempt to avoid detection of illegal drugs in the urine or bloodstream, or purposeful over-hydration.
It is recommended that the color of the urine not be greater than 3 on this chart, which signifies dehydration
Bright Yellow Urine:
Bright yellow urine is often the result of riboflavin, a byproduct of Vitamin B2.
Dark Yellow Urine: Dehydration
Dark yellow or tea-colored urine usually signifies dehydration. Bright yellow or light orange urine may appear if you are taking a multi-vitamin or vitamin B-12 supplement since excessive vitamin B-12 will be removed from the bloodstream and will appear in the urine.
Orange Urine: A Side Effect of Pyridium (Medication)
Orange urine may be frightening to see, but often it is a side effect of medications or dyes present in a food item you ate. Sometimes, however, it signifies more. If an individual experiences chronic orange urine, this may be a sign of liver disease, with the orange color being due to the presence of increased levels of bilirubin in the urine, and may include jaundice (yellowing of the skin or whites of the eyes). Fatty liver, non-alcoholic fatty liver disease, alcoholism, cirrhosis, liver flukes, or viruses such as hepatitis A, B, C, D or G may cause this condition.
Medications that may cause orange urine include:
Rifampin
Phenazopyridine
Pyridium
Green Urine: Side Effect of Propofol Medication
Green urine is usually due to the consumption of foods like asparagus or foods containing green dyes. There are some medications, however, they may result in the production of green urine, one of them being propofol, a sedative.
Blue Urine: Side Effect of the Dye Injected Into the Veins for an Intravenous Pyelogram to View the Urinary Tract
Special dyes containing blue pigments, such as methylene blue, inserted into the veins for pyelograms for looking at internal structures, may cause blue urine. Other things that may cause blue urine are foods or beverages containing blue dye.
Pyelogram
Clear Urine: May be a Symptom of Diabetes Insipidus
Diabetes insipidus is a type of diabetes that produces massive amounts of dilute urine. It also causes the individual to feel excessively thirsty. As much as 20 liters of urine per day can be lost in this condition! This can cause severe dehydration in some individuals, leading to seizures if severe enough. There are basically four subtypes of diabetes insipidus:
Central Diabetes Insipidus
Individual lacks the hormone vasopressin, an antidiuretic hormone
Nephrogenic Diabetes Insipidus
The kidneys are not responding the way they should to the hormone vasopressin
Dispogenic Diabetes Insipidus
Abnormal thirst mechanisms in the hypothalamus
Gestational type occurs only during pregnancy
Some types of nephritis
Treatment includes fluids to replace fluid and electrolytes lost. Central and gestational DI are treated with desmopressin, whereas nephrogenic DI is treated by identifying and treating the underlying cause, followed by treatment with a thiazide, aspirin or ibuprofen. Patients are monitored regularly for loss of potassium leading to hypokalemia, loss of sodium leading to hyponatremia, loss of magnesium, calcium or phosphate.
Some of the causes could include a malignancy or benign tumor in the pituitary gland or brain, head trauma or surgery, but most of the time there is no known cause.
Pale urine with frequency, particularly at night (nocturia) is a symptom of Diabetes insipidus and could be due to excess hormone release from the adrenal glands that sit atop the kidneys.
Pyuria: Symptom of Bacterial Urinary Tract Infection
Pyuria is pus in the urine, and the urine will appear cloudy, thick, and green to green-yellow. This is a result of bacteria, nitrates, and white blood cells (leukocytes) in the urine. It will often have a strong odor of ammonia as well. This typically signifies a urinary tract infection, whether it be a bladder, cystitis, urethral, or kidney infection.
Pyuria (pus and white blood cells and cellular debris), resulting in a thick, dark yellow-to-green colored urine,By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17978816
Hematuria:
Hematuria is blood in the urine. Blood in the urine that is visible to the naked eye is referred to as "gross hematuria", meaning that it is macroscopic. Blood in the urine that is not visible to the naked eye but seen microscopically is referred to as "microscopic hematuria".
Brown urine is due to a condition called rhabdomyolysis, which is the breakdown of myoglobin in muscle cells, and is usually due to trauma, cardiac myopathy, hyperthermia, problems with the vascular system, electrical burns, thermal burns, or other underlying illnesses in which muscles are damaged. It may also be caused by a condition known as Gilbert's syndrome (genetic liver disorder), McArdle's disease (glycogen storage disease), or it may be caused by a serious genetic disorder called porphyria. Other rare conditions that cause this are enzyme deficiencies, including those of phosphofruktokinase, lactate dehydrogenase, or others.
Occasional pink urine may resemble hematuria but is due to the consumption of beets
Hematuria: Blood in the Urine;
Hemoglobinuria: Blood in the Urine (RBC's lysed and hemoglobin has been released into the urine). Causes include a number of conditions, such as glomerulonephritis, porphyuria, the presence of kidney stones, trauma, and others.
Blood in the urine due to trauma, image By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=12853647
Myoglobinuria due to rhabdomyelitis (break down of muscle fibers), By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11309876
Bilirubinuria: Bilirubin in the Urine: A little bit of yellow foam on the top
By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11309876
Proteinuria: A lot of foam like egg-white when shaken
Proteinuria may signify a diet high in protein, or something more serious such as Diabetes mellitus or kidney disease. Proteins normally do not spill over into the urine and when they do, it creates a layer of bubbles/foam on top of the urine when shaken. This foam is due to the presence of the protein albumin, a serum protein in humans that is also the same protein found in egg whites.
Black Urine (Very Rare): Melanoma or Acute Intermittent Porphyuria
Black urine is a very rare condition associated with melanoma, aggressive cancers associated with the pigment melanin.
URINE ODOR:
Urine odor is part of the macroscopic examination as well, and can signify a variety of conditions:
Ammonia/pungent: either the urine sat out too long unrefrigerated (should be refrigerated within 2 hours if not tested right away), or a urinary tract infection or some types of kidney stones that are associated with bacteria
Sweet: Diabetes (excess glucose in the urine) or kidney disease
Sweet like maple syrup: Maple Syrup Urine Disease
Asparagus: due to the presence of asparagusic acid found in asparagus
Some foods or spices can cause the urine to take on a smell of such, and include things like onion, garlic, curry, turmeric, alcohol, coffee, tuna fish, saffron
URINE TURBIDITY:
The urine is visually observed for clarity and turbidity during this portion of the examination. If you can see right through urine held up in front of newspaper print, and it is clear and easy to read, the urine has good clarity. If you cannot clearly see the print, however, and the urine is fuzzy or cloudy, then it is considered to be turbid.
Turbidity (cloudiness) may signify a urinary tract infection or some other disorder affecting the urinary system. The presence of urinary crystals such as calcium phosphate may also result in turbidity or cloudiness.
The microscopic examination is performed after the macroscopic examination, and along with the urine test strip evaluation, and is important in the confirmation of the presence of abnormal cells, casts or crystals in the urine.
The standardized quantitative microscopic examination is made on urine sediment. Analyzation includes looking for increased numbers of red blood cells, white blood cells, casts or crystals in the urine, which may indicate disease presence or progression, and aids in initial diagnosis and monitoring of renal disease.
Standards for accuracy and precision and consistency of this examination are established in laboratory protocols for manual preparation of the urine sediment, including what supplies to use, the sequence of steps, timing, and equipment. Each laboratory is different. Refer to your laboratory's SOPs for more information. A broad overview will be discussed below.
Factors Requiring Standardization in the Microscope Examination:
Urine Volume Used (Ex: 1o mL, 12 mL, 15 mL)
Speed of Centrifugation (Ex: 400 or 450 x g)
Time of Centrifugation (Ex: 5 min.)
Concentration of Sediment (Ex: 10:1, 12:1, 15:1)
Volume of Sediment Examined
Result Reporting (Depends on Equipment, Software, Format, Terminology, Reference Intervals, Magnification)
Specimen Volume: The typical volume of urine recommended for a routine urinalysis is 12 mL, but the typical reference range is 10-15 mL from a well-mixed specimen. In pediatric collections, this is not usually possible, so the volume may be reduced to 6 mL. If <3 mL is received, some laboratories will go ahead and perform the microscopic examination without concentration of the sediment, but this must be notated or documented.
Centrifugation and Concentration: Well-mixed urine is poured into a centrifuge tube, covered, and centrifuged at 400-450 x g (1200 to 15oo RPM, depending on the type of machine) for about 5 minutes. This enables optimal sediment concentration and does not damage the formed elements, which are fragile. After centrifugation, the covered urine specimen should be carefully removed and the sediment concentrated, depending on your laboratory's manual. This typically ranges from 12:1 to a 30:1 concentration. Remove the supernatant by decanting it until about 1 mL of urine is retained, then use a pipette to gently resuspend the sediment.
Viewing the Sediment: The microscopic examination of urine should be performed if possible on a centrifuged specimen with the supernatant removed and the button (1 mL) resuspended for concentration. Centrifugation of urine should be at about 2,000 rmp for 5 minutes. For the microscopic examination, a standard slide should be used or a semiautomated microscope system can be used. Aspirate the concentrated urine into the viewing chamber or slide with coverslip and view immediately. At least 10 low-power or 10 high-power fields should be viewed. Partially close the iris diaphragm and adjust the condenser down so that the ideal medium contrast will be provided for viewing the sediment so that there won't be too much light or too little light.
Under the 10x objective, you should look for casts, crystals, and elements, then switch to high dry 40x to look for other structures.
Qualitative per Field of View:
Crystals
Mucus
Bacteria
Enumerating:
RBCs
WBCs
Casts
Quantitating:
Rare (1+)
Few (1+)
Moderate (2+)
Many (3+)
Packed (4+)
Stains:
Sternheimer-Malbin: supravital stain used for cellular structures and formed elements, and consists of crystal violet and safranin
Note that in strongly basic/alkaline urine, the stain can precipitate, obstructing views of sediment components
Squamous epithelial cells show up very well in this stain
0.5% Toluidine Blue: metachromic stain to enhance nuclear detail of cells and to differentiate WBCs and RT epithelial cells
2% Acetic Acid: makes leukocyte and epithelial cell nuclei stand out and lyses RBCs
Fat Stains (Sudan III, Oil Red O): stains fats that may be present in urine (oval fat bodies) an orange-red color
Prussian Blue Stain: used to identify hemosiderin (iron) (free-floating, in casts, or in epithelial cells)
Hansel Stain: aids in the ID of eosinophils (allergic reactions, parasites, inflammation)
Gram Stain: aids in the ID of bacterial and fungal casts, or bacteria or fungi in the urine (infection)
Enhancing Urine Sediment Visualization:
Phase Contrast Microscopy can be used to aid in the visualization of hyaline or transparent mucus or casts or bacteria. Stains also help differentiate formed elements in urine.
Polazarizing Microscopy can be used to visualize cholesterol crystals in urine ("Maltese Cross").
Interference Contrast Microscopy can be used to enhance images of formed elements by producing 3D images.
Formed Elements in Urine:
Casts-cylinder-shaped bodies with a glycoprotein matrix, which form in the lumen of the renal tubules and become flushed out with the urine.
Microbes-bacteria, yeasts, parasites, or trichomonads present in the urine, which may be causing infection
RBCs
WBCs
Epithelial Cells
Artifacts in Urine:
Menstrual Blood
Starch Granules
Sperm
Fibers (Threads, Hair, Diaper Fiber)
Reference Intervals for Microscopic Examination of Formed Elements:
RBCs: 0-3 per HPF
Hypertonic Urine: smaller and crenated with spicules
Hypotonic Urine: "ghost cells" without hemoglobin (empty circles)
Increased numbers, along with RBC casts, indicate renal bleeding (glomerular or tubular) and proteinuria
Increased numbers without RBC casts or proteinuria indicate contamination with menstrual or hemorrhoidal blood, or bleeding below the kidney
Rule out: pyelonephritis, glomerulonephritis, cystitis, calculi, hypertension, appendicitis, tumors, trauma strenuous exercise, drugs, smoking, toxic drug reaction or allergy
WBCs: 0-8 per HPF
Neutrophils (most often observed; infection or inflammation)
When seen with casts, there may be an upper UTI (kidney infection) and the urine may appear cloudy and have a strong, foul odor
Hypotonic Urine: swollen, spherical balls that lyse in 2-3 hours at room temp ("glitter cells")
Hypertonic Urine: smaller cells
Casts: 0-2 hyaline or finely granular per LPF
Epithelial Cells:
Squamous: Few/LPF
Most common
Line the urethra and vagina
Large, uneven cells with ruffled edges and a small, central nucleus; Resemble "fried eggs"
Typically not clinically significant
Increased numbers may indicate poor collection and contamination (not a "clean catch")
Transitional/Urothelial: Few/HPF
Line bladder, ureters, renal pelvis, majority of the male urethra
Have different sizes and shapes
Increased numbers with infection or inflammation of the bladder, ureters, renal pelvis, or male urethra
May occur in clusters or sheets after catheterization or cystoscopy
Types:
Round:
Most common
Central nucleus
Smaller than the squamous epithelial cell
Line the bladder and line the proximal urethra in men
Smaller ones line the deeper epithelium and the renal pelvis
Caudate:
Look like they have a "tail"
Line the deep layers of the bladder
Some have two nuclei
Asymmetric ones may indicate a transitional cell carcinoma
Renal: Few/HPF
From kidney nephrons or collecting ducts
Appear with ischemic events, such as trauma, shock, a stroke, sepsis, anoxia, or toxins such as heavy metals, poisons, drugs (Ex: aminoglycosides, salicylates), hemoglobinuria, myoglobinuria
Bacteria and Yeasts: Negative/HPF
Abnormal Crystals: none/LPF
Red Blood Cells:
Hematuria is the presence of blood in the urine. It may be microscopic, macroscopic, or both. The image below shows what red blood cells (erythrocytes) in the urine look like. More than 3 red blood cells/HPF should never be present in the urine unless a female is on her menstrual period (reference is 0-3 cells/HPF). Other than that, blood in the urine is not normal and should be investigated as to why. Look for a positive plasma protein test for true hematuria in large amounts.
Lysed red blood cells are called "ghost cells" or "shadow cells", because they have burst and released their hemoglobin into the urine, causing them to appear as empty shells and are simply the red blood cell membranes left behind. This will happen in urine that is alkaline or in hypertonic urine.
Kidney stones, strenuous exercise, trauma, urinary tract infections, inflammation, and other underlying illnesses may cause blood in the urine.
Red blood cells in a urine sample,By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5652416
Dysmorphic RBCs
White Blood Cells and Bacteria:
White blood cells (leukocytes) are usually not present in the urine (>0-8/HPF) unless there is an underlying infection or inflammatory condition in the urinary system. The average normal urine contains up to about 2 WBC/HPF. WBCs in urine appear larger than RBCs, and are usually round, dull gray, and found in singles or clumps. They will typically contain granules or lobules of the nucleus. In hypotonic urine, the lobules and granules are easily seen, however, they tend to shrink in hypertonic urine. If the urine is too hypotonic, the WBCs may lyse by as much as 50% at room temp. within an hour. In dilute or hypotonic urine, the granules will start moving via Brownian motion, causing the cells to "glimmer", so they are referred to as "glitter cells". They occur in a variety of conditions, especially pyelonephritis.
Neutrophils present in the urine indicate the presence of infection if seen along with bacteria in the urine, or inflammation. The presence of eosinophils, on the other hand, may indicate allergic reaction (allergic interstitial nephritis) or atheroembolic disease. Sometimes their presence will produce pyruia, or pus in the urine, causing the urine to have a "milky" appearance. Appendicitis and pancreatitis can also cause this, as can acute glomerulonephritis, lupus nephritis, dehydration, stress, fever, renal tubular acidosis, or irritation to the ureter, bladder, or urethra. When many WBC clumps are present in the urine, this can indicate renal origin.
Microscopic urine sediment, including epithelial cells,By J3D3 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18682766
White blood cells in urine,By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5652287
Numerous white blood cells in the urine, By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5652379
Bacteria and white blood cells in the urine,By Steven Fruitsmaak - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3277713
Epithelial Cells in Urine:
Epithelial cells are commonly seen in the urine and may originate from any site in the genitourinary tract. Normal sloughing off of old, worn cells is normal in smaller numbers, however, in larger numbers it may indicate inflammation or irritation. There are three types of epithelial cells in the urinary tract: 1) squamous, 2) transitional, 3) renal tubular.
1) Squamous:
Look like "fried eggs"
Large, flat, irregular
Small, central nucleus
Abundant cytoplasm
Edge may be folded/rolled up into a cylindrical shape
Mainly found in the urethra and vagina
Usually the result of contamination from the vagina or vulva in female urine
2) Transitional:
2-4x the size of a WBC
Round, pear-shaped, or tail-like projections may be observed
1-2 nuclei
Line the renal pelvis all the way to the upper urethra
3) Renal Tubular:
Just a bit smaller than a WBC
1 large, spherical nucleus
Flat, cube-shaped, or columnar
Resemble "eyeballs"
In increased numbers, may indicate renal tubular damage
Pyelonephritis
Acute tubular necrosis (burns, trauma)
Salicylate intoxication
Kidney transplant rejection
Pyuria with red blood cells, white blood cells, and an epithelial cell; By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5652310
Epithelial Cells
Renal Transitional Epithelial Cells (RTE cells) By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5652349
Bence-Jones Protein:
The presence of Bence-Jones protein in urine is serious because it may be indicative of multiple myeloma, lymphoma, leukemia, or Waldenstrom's macroglobulinemia and may be seen in renal failure or end stage renal disease when kidneys have sustained long-term damage. It is also sometimes seen in cases of osteogenic sarcoma, amyloidosis, or other malignancies.
Bence-Jones protein is made up of dimers of kappa or lambda light chains from immunoglobulins. Overproduction of these chains may be filtered at the glomerulus and spill over into the urine.
By Alex McPherson, University of California, Irvine - http://images.nigms.nih.gov/index.cfm?event=viewDetail&imageID=2399, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5218720
Crystals:
Crystals in the urine is known as "crystalluria". Some types of crystals are associated with acute urate nephropathy and other types (like calcium oxalatin) are associated with ethylene glycol poisoning (antifreeze). Crystals are not typically seen in freshly voided urine. If the urine sits awhile, they will form, and they are pH-dependent. If urine is supersaturated or super soluble, crystals may occur. They are associated with kidney or urinary tract precipitation causing the formation of kidney stones, but many of the typical crystals seen are not of clinical significance. Conditions that are of clinical significance include the following:
Kidney stones (calculi)
Metabolic disorders
Regulation of medication
The most clinically significant crystals include:
Leucine
Tyrosine
Cystine
Cholesterol
Sulfa
Acidic Urine:
Uric acid crystals
Calcium oxalate
Amorphous urates
Calcium sulfate
Sodium urate
Hippuric acid
Cystine
Leucein
Tyrosine
Cholesterol
Sulfa
X-ray dye
Bilirubin
Ammonium biurate
Alkaline (Basic) Urine:
Triple phosphate
Calcium carbonate
Ammonium biurate
Amorphous phosphates
Calcium phosphate
Calcium oxalate can form
Amorphous Urates and Uric Acid Crystals:
Uric acid crystals form many different shapes, but are typically seen as diamond shapes or as rhomboid prisms. They do not necessarily indicate a pathological condition, but pathological conditions are associated with include:
gout
high purine metabolism
nephritis
acute febrile conditions
Lesch-Nyhan syndrome
The image below shows many uric acid crystals along with amorphous urates, which are salts of sodium (Na+), potassium (K+), magnesium (Mg+) and calcium (Ca++). They are granular and they don't have any clinical significance. .
By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30193714
Typical uric acid crystal in urine
Hippuric Acid Crystals:
Hippuric acid crystals are yellow-brown or colorless. They are toothpick-like, elongated prisms. Sometimes they may form plates. They are very thin and needle-like and they usually form clusters. They are very rarely seen in the urine, and they don't have any clinical significance.
Monosodium Urate Crystals:
In urine, sodium urates are amorphous or found as needle-like crystals in clusters or sheaves. In urine, they have no clinical significance as they do in body fluids.
By Gabriel Caponetti - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31339326
Calcium Sulfate Crystals:
Calcium sulfate crystals have no clinical significance, but they are long, thin and colorless needles and look just like calcium phosphate. They are rarely seen in the urine.
Struvite Crystals (Triple Phosphate):
Struvite crystals are made of magnesium ammonium phosphate, a phosphate mineral. These crystals readily form in the urine of humans or animals containing ammonia-producing microbes. They are associated with alkaline/basic urine and diets high in magnesium. It is also associated with some types of kidney stones in humans. Struvite stone formation is caused by ammonium-producing bacteria such as Proteus species, Klebsiella oxytoca, Staphylococcus species, Mycoplasma or Pseudomonas aeruginosa. These bacteria hydrolyze urea to form ammonia and raise the pH of the urine to near neutral or to basic/alkaline values. Struvite stones look like actual stones or pebbles. They are also seen in chronic pyelitis, chronic cystitis, enlarged prostate, and conditions that cause urine retention in the bladder.
Struvite or magnesium ammonium phosphate,By Joel Mills - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1607945
Amorphous Phosphates:
Amorphous phosphates are glassy-like precipitates that form in alkaline urine. Phosphate salts are what make up amorphous phosphates, and they are often found in the urine. They are granular without particular shape and are soluble in acetic acid. They have no clinical significance.
Struvite crystals are associated with a high pH urine. In this case, these crystals were associated with a urine pH of 9.0 (alkaline or basic).By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20870070
Struvite stones of various sizes;By Joel Mills - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=951812
Calcium Oxalate Crystals:
Calcium oxalate is a calcium salt that forms envelope-shaped crystals in the urine. It is associated with the formation of kidney stones. They are also seen in the urine of individuals who have undergone ethylene glycol poisoning (antifreeze). They are occasionally seen in large numbers in patients with liver disease, diabetes mellitus type 2, or severe chronic renal disease. They are also present in urine following a large intake of vitamin C, due to production of oxalic acid following the breakdown of ascorbic acid found in vitamin C. The crystals are colorless.
There are two forms of calcium oxalate crystals:
Calcium oxalate monohydrate
vary in shape
dumbell-shaped
spindle-shaped
oval-shaped
shaped like a picket fence in ethylene glycol poisoning
Calcium oxalate dihydrate: octahedral form
grow at any pH
naturally occur in normal urine
envelope-shape
About 80% of kidney stones are made of calcium oxalate. They tend to form in acidic urine.
Calcium Oxalate Monohydrate crystal (dumbbell-shaped) and Calcium Oxalate Dihydrate crystal (envelope-shaped), along with many red blood cells seen in a urine sample. These crystals are a major component of KIDNEY STONES. They grow at any pH.By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20865259
By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20865307
By NASA/JSC - http://www.nasa.gov/images/content/152115main_renal6_720x515.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4948006
Calcium oxalate kidney stone;By GrammarFascist - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44053196
Calcium oxalate kidney stones;By Joel Mills - Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=927204
The surface of calcium oxalate kidney stones;By Kempf EK - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17967284
Uric Acid Crystals:
High levels of uric acid in the blood may be associated with the formation of kidney stones. They are seen secondary to obesity, insulin resistance, and metabolic syndrome. This results in an increase in the acid load on the kidneys. The urine becomes very acidic, uric acid is insoluble, and it precipitates (forms a solid) in urine. This is how the kidney stones form, and are seen in high prevalence in individuals with Diabetes mellitus type 2.
Uric Acid crystals in a pH of 5.0, and a few amorphous crystals as well.By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30193714
Uric Acid Crystals
By Doruk Salancı - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30742375
Uric acid kidney stone;By Monster4711 - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=22096282
Calcium Phosphate Crystals: Single and Rosette Forms (Needle-Like Sheaths)
Calcium phosphate crystals form long, thin needles in rosette shapes, star shapes, or bundles/sheaves. Sometimes they form plates that float on top of the urine. They're soluble in acetic acid. They may be present in normal urine, however, they are also linked to the formation of calculi.
By Hofmann, Karl Berthold, 1842-1922. [from old catalog];Ultzmann, Robert, 1842-1889, [from old catalog] joint author;Brune, T. Barton, [from old catalog] tr;Curtis, Henry Holbrook, 1856-1920, [from old catalog] joint tr - https://www.flickr.com/photos/internetarchivebookimages/14778955602/Source book page: https://archive.org/stream/analysisofurine00hofm/analysisofurine00hofm#page/n322/mode/1up, No restrictions, https://commons.wikimedia.org/w/index.php?curid=43245337
Tyrosine and Leucine Crystals:
Leucine crystals are clinically significant. They are associated with Maple Syrup Urine Disease. They are also seen in individuals with liver disease. Tyrosine crystals are fine needles found in sheaves or clusters, and leucine crystals are spherical, highly refractile, yellow or brown spheres with striations that are radial or concentric. Tyrosine crystals are seen in severe liver disease, tyrosinosis or Oasthouse urine disease.
Cholesterol Crystals:
Cholesterol crystals are flat plates with notched edges and may be seen as a film on the top of the surface of the urine. This may indicate breakdown of tissue in excess and are seen in nephritis or nephrotic conditions or in chyluria due to abdominal or thoracic obstruction to lymph drainage by tumors, filariasis, or enlargement of the abdominal lymph nodes.
Sulfa and Drug Crystals, Including X-Ray Dye:
Patients on sulfa drug therapy or who have been exposed to X-ray dyes may form needle-like crystals in their urine, which are found in bundles or sheaves. In cases of bilirubinuria, bilirubin may also crystalize as needles or granules, but there is no clinical significance to them.
Ammonium Biurate Crystals:
"Thorny apple" appearance and only clinically significant in fresh urine due to dehydration of the patient
Ammonium Biurate,By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=7777797
Cystine Crystals:
Cystine crystals are colorless, hexagon-shaped, refractile crystals found in the urine of individuals with underlying kidney disorders, including polycystic kidney disease, and is referred to as cystinuria. It is a rare, autosomal recessive disorder. These types of crystals associated with cystine stones are rare, comprising just 1-2% of all kidney stones. When found in the urine, their presence is always clinically significant!
Cholesterol crystals are found in urine of individuals with lipiduria. They are often associated with "Maltese Crosses" under polarized light microscopy.
Cholesterol crystals in polarized light seen along with a "Maltese Cross" (lipiduria);By Ed Uthman from Houston, TX, USA - Cholesterol Crystals in Synovial Fluid (compensated polariscopy)Uploaded by CFCF, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=30104385
Cholesterol Crystal with Notched Edges,By The Armed Forces Institute of Pathology - Image and description are from the AFIP Atlas of Tumor Pathology, according to entry # 406090 in Pathology Education Instructional Resource. The Armed Forces Institute of Pathology Electronic Fascicles (CD-ROM Version of the Atlas of Tumor Pathology) contains U.S. Government work which may be used without restriction.[1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=3777545
Casts:
Urinary casts form in the distal or collecting tubules (lumen) of the kidneys, which gives them their tube-like shape. Precipitation or gelation of the Tamm-Horsfall mucoprotein is responsible for the molding of the casts, which may then cause cells to "stick" to them inside the protein matrix. This is where the urine is most concentrated and acidified. Casts are always renal in origin. Acidic pH contributes to their formation. Plasma proteins contribute, as do excessive physical activity, fever and dehydration. Factors involved in cast formation include the following:
pH more acidic
urinary stasis
high solute concentration, particularly of plasma proteins
abnormal protein constituents
excessive physical activity
fever
dehydration
Casts may indicate:
renal inflammation
tubular damage
glomerular damage
renal infection
Casts are classified based upon:
appearance
size
type of cells they contain
Types of casts include:
hyaline
red cell
white cell
epithelial cell
granular
coarse
fine
waxy
fatty
broad
mixed
Red blood cell casts:
Acute Glomerulonephritis (post-streptococcal)
Severe pyelonephritis
Right-sided congestive heart failure
Renal vein thrombosis
Periarteritis nodosa
Indicate renal hematuria
Always pathologic
Vasculitis
Nephritic syndrome
Urinary tract injury
Malignant hypertension
Granulomatosis
Systemic lupus erythematosis
Goodpasture's syndrome
Renal infarction or trauma
Bacterial endocarditis
Yellow-brown in color
Cylindrical with jagged edges
A few cells to jam-packed
Reddish-brown granular cast indicates a hemoglobin or blood cast
These type are always abnormal (never normal)
White blood cell casts:
Severe pyelonephritis (kidney infection)
Exudative glomerulonephritis (post-streptococcal)
Acute interstitial nephritis (may be due to allergic reaction)
Lupus nephritis
Nephrotic syndrome
Inflammation or infection
There will be a presence of hyaline matrix along with the white blood cells, mostly PMNs
Epithelial cell casts:
Sticking together of epithelial cells that have shed the tubule lining
Contain large, round nuclei
Result of urinary stasis and desquamation of renal tubular epithelial cells
Seen in acute tubular necrosis
Seen in toxic ingestion of chemicals (mercury, aspirin, antifreeze)
Seen in viruses like hepatitis of the liver or cytomegalovirus (CMV)
Sloughed off in clumps/sheets
Granular casts:
Acute tubular necrosis ("muddy brown cast")
Chronic renal disease
May just be due to strenuous exercise
Second most common type seen
Formed by breakdown of cellular casts or
Formed by clumping of plasma proteins
May be fine or coarse
Resemble cigars
Waxy casts (Broad casts):
Chronic renal disease (severe)
Nephrotic syndrome
Low urine flow
Associated with renal failure and malignant hypertension
Renal amyloidosis
Diabetic nephropathy
Tubular inflammation
Renal allograft rejection
Large/wide due to urine stasis in renal tubules
Round, high refractive index
Hard, often broken, cracked, serrated, rough edges
Yellow, gray, or colorless
Smooth, homogenous in appearance
Possibly form from degeneration of granular casts
Hyaline casts:
Usually normal, seen in dehydration or strenuous exercise in increased numbers
Composed of gelled Tamm-Horsfall mucoprotein
Most common type seen
Most frequently seen
Low refactile index (view under low light)
Colorless, transparent, homogenous, rounded ends
A few are normal in urine
Fatty casts:
Formed from breakdown of epithelial cells, which are rich in phospholipids
Fat-globule inclusions or free fat droplets or oval fat bodies incorporated into casts
Consist of triglycerides
Will stain well with Sudan III or Oil Red O
Tan-yellow color
Associated with the "Maltese cross" sign in polarized light
Sign of high protein nephrotic syndrome
Associated with fatty degeneration of the tubular epithelium or degenerative tubular disease
Found in diabetic glomerulosclerosis
Lipoid nephrosis
Chronic glomerulonephritis
Kimmelstiel-Wilson syndrome
Lupus (autoimmune)
Toxic renal poisoning (drugs or chemicals)
Pigment casts:
Break down of toxins, drugs, or pigments
Hemoglobin breakdown (seen in hemolytic anemia)
Myoglobin breakdown (seen in rhabdomyolysis)
Bilirubin breakdown (seen in liver disease)
Urinary drugs cause them as well
Bacterial casts:
Pyelonephritis (kidney infection)
Bacteria, WBCs, RBCs, and WBC casts
They are rare
Types of Casts Seen in the Urine. Matrix: Tamm-Horsfall Mycoprotein
View urine microscopic exam under phase-contrast so the hyaline portions will stand out;By Steven Fruitsmaak - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3277350
Nephrotic Syndrome,By Nephron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17547364
Hyaline Casts:
Erythrocyte Casts:
Leukocyte Casts:
Renal Epithelial Casts:
Granular Casts:
Waxy Casts:
Fatty Casts:
Bacterial Casts:
Pseudocasts:
Phosphate crystals
Mucus
Other Urine Components:
Yeast cells (budding or pseudohyphae)
Oval, smooth, colorless cells
Seen in UTI
Seen in diabetic patients
May be due to contamination by vaginal skin
C. albicans is the most common yeast found in the urine
Cylindroids
Look like casts or mucous
Usually hyaline
Spermatozoa
May be present in the urine of men after a seizure, a disease or inflammation of a genital organ, spermatorrhea or other
Mucous Threads
These are long, thin, wavy, ribbon-like threads
A few are normal
Increased numbers seen in inflammation or irritation
Oval Fat Bodies
Free Fat Droplets
Artifacts
Diaper or other fibers
Starch
Maltese Crosses
Cornstarch
Oil droplet
Lubricants
Hair
Talcum Powder
Glass
Vegetable fibers
Muscle fibers
Tissue strands
Air bubbles
TESTS: Urinalysis Test Strips, Specific Gravity, Ketones, Glucose, Clinitest for Reducing Substances, Proteins, pH, Bilirubin
Urine Test Strips: Chemstrips or Multistix
Urine test strips are used during urinalysis to test a number of different things on the urine at the same time. They are also known as reagent test strips and commonly used ones include Chemstrips or Multistix. These narrow strips are impregnated with small pads containing reagents that allow for different reactions after dipping the strip in urine. Different pads (tests) are read at different times, so it is important to adhere to this. The strip is compared to a color coded chart provided on the jar by the manufacturer.
Care must be taken with the dipsticks to ensure reliable and accurate results. Precautions must be taken to help maintain the reactivity of the reagents. These include the following:
Avoid exposure to moisture and direct sunlight
Avoid heat
Avoid volatile substances
Store in original container at room temperature
Keep the dessicant in the package
Remove only what you need, then tightly close the container
Make sure the color blocks resemble the negative blocks on the color chart
Do not use past expiration date
Urine should be at room temp. prior to testing
pH:
Normal range: 5.5-7.0
Average: 6.2 (slightly acidic)
Too acidic: hyperuricosuria (may contribute to the formation of certain kidney stones, including uric acid in the kidneys, ureters or bladder) (see image under kidney stones)
A diet high in meat, protein, dairy can also cause the urine to become more acidic
Alcoholism can also cause the urine to become more acidic
Medications can lower the pH of urine (ammonium chloride, chlorothiazide diuretics, methenamine mandalate)
Too alkaline/basic: due to the presence of bacteria, nitrate, or ammonia or some kidney stones associated with bacteria like Proteus species or Pseudomonas aeruginosa
Diets high in fruits and vegetables can make the urine more basic/alkaline
Medications can raise the urine pH (sodium bicarbonate, potassium citrate, acetazolamide)
Leukocytes:
If their presence is positive on the urine test strip, this indicates an infection or inflammation is present (leukocyturia)
This strip test detects the presence of granulocytes in the urine
This strip contains buffered indoxyl carboxylic acid ester and diazonium salt
Granulocyte esterases catalyze a conversion of indoxyl carboxylic acid ester to indoxyl, which reacts with diazonium salt and produces a change in color
Large amounts of ascorbic acid, gentamicin or cephalexin levels, or urinary albumin may interfere with the test
Orange nitrofurantoin medicine interferes with the test
Nitrites:
If positive, their presence indicates the presence of bacteria and is usually indicative of an infection (nitrituria)
Proteins:
If positive, this indicates proteinuria, microalbuminuria, or albuminuria, and may indicate Diabetes mellitus, kidney disease, recent strenuous exercise, or other underlying conditions
Ketones:
If ketones are present in the urine, this may indicate dehydration, or something more serious such as Diabetes mellitus type 1 or 2
Ketonuria is the presence of ketone bodies in the urine
Ketosis is a mild form of ketoacidosis, and usually just happens temporarily when you skip a meal/fast, go on a low carb diet, or consume alcohol
Ketoacidosis is a critical condition of a Diabetic individual where the body/blood has become too acidic and must be treated as soon as possible to prevent loss of consciousness or falling into a coma (life-threatening condition)
Can develop quickly in type 1 Diabetes (<24 hours)
Can rapidly progress
The body is not making enough insulin
Symptoms: feeling extremely thirsty, very dehydrated, frequent urination, nausea, vomiting, abdominal pain, fatigue, shortness of breath, a fruity smell on the breath and sometimes in the urine, confusion and difficulty concentrating
Ketone bodies may be present during starvation, a skipped meal (fasting), low carb diet, prolonged vomiting due to acute illness, stress, or an eating disorder such as anorexia nervosa or bulimia
Blood:
If positive, may either be due to menstruation (females), urinary tract infection, kidney stone, inflammation, trauma, strenuous exercise, or cancer/tumors
Specific Gravity:
Urine density
Interferences:
Vitamin C (Ascorbic Acid)
High concentrations of this can interfere with the following tests:
Glucose
Occult blood
Bilirubin
Nitrite
If interfering levels are present, repeat the urinalysis at least 24 hours after the last dose of vitamin C
Chemstrips
By J3D3 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18675760
Ketostix test strips for ketonuria; By Colin - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4861250
By J3D3 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18682507
By J3D3 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18676004
By Grook Da Oger - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4567043
Glucose/Ketones:
By Caipira - photo taken by Caipira, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3013056
Acetest:
The acetest is used as a confirmation test for the presence of ketone bodies in the urine, serum, plasma or whole blood. The tablets are sensitive to moisture and light.
STEPS:
Put an Acetest reagent tablet on a square of paper
Add 1 drop of urine, serum, plasma or whole blood
Wait 30 seconds
Quantitate as: negative, small, moderate, or large amount based on the color scale shown below
Ictotest:
This test is used for the detection of old, worn red blood cells in the urine. It is a confirmation test for the presence of bilirubin in the urine. The tablets are susceptible to moisture and light and will break down and crumble and become discolored in the presence of moisture.
STEPS:
Add 10 drops of urine to a square
Place the Ictotest reagent tablet on the square
Add 1 drop of sterile water and wait 5 seconds
Add a 2nd drop of sterile water and let it run off
Read at 60 seconds
If the tablet turned blue/purple, it is positive for the presence of bilirubin in the urine
Hemoglobin Test:
This test is important for testing for hemolysis in the blood vessels. This means that capillaries have ruptured in the glomerulus of the kidneys, resulting in a hemorrhage in the urinary system, causing hemoglobin to show up in the urine.
Clinitest for Reducing Substances:
STEPS:
Add 5 drops of urine to a sterile test tube
Add 10 drops of sterile water
Place a Clinitest reagent tablet to the mixture with tweezers and wait until it stops boiling
Read after 15 seconds
Refer to the color chart for quantitation
The Clinitest or Benedict's Test for Reducing Sugars is both quantitative and qualitative. It is qualitative in that any color ranging from green to yellow to orange to red indicates a positive test. It is qualitative in that the colors are associated with levels of reducing sugars, ranging from trace, to small, to moderate, to large amounts.
The blue tests are negative, the green tests are positive (trace), the yellow tests are positive (small-to-moderate), the orange tests are positive (moderate)
By Thebiologyprimer - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=32341865
SSA Test:
STEPS:
Add 3 mL of 3% SSA reagent to 3 mL of centrifuged urine
Mix
Look for turbidity (cloudiness)
Specific Gravity and Refractometers:
Specific gravity measures the density of urine. The normal range of specific gravity of urine is 1.003-1.035. Anything less than that means that the urine is dilute and not concentrated enough. Anything higher than that means that the urine has a high specific gravity/density and is too concentrated, and there may be too much protein or glucose in the urine, or bacteria and pus in the urine. Anything deviating from average may signify some type of urinary disorder.
Urine specific gravity should range between 1.000 and 1.030 for adults; By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5655038
By Pugwash21C - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=25633996
By User:Kandschwar - Own work, CC BY-SA 2.0 de, https://commons.wikimedia.org/w/index.php?curid=2801282
URINE CULTURE AND PLATING URINE:
Urine is plated on urine cultures to detect bacteriuria using the semi-quantitative method for colony count. The plates used include a 5% Sheep's Blood Agar plate for observation of hemolysis patterns, and the MacConkey plate, for determination of lactose-fermenting and non-lactose-fermenting Gram-negative rods. The MacConkey plate includes crystal violet and bile salts to enhance the growth of Gram-negative organisms, and prevent the growth of Gram-positive organisms, and it contains lactose sugar for fermenters. A pH indicator (phenol red) is also included. Upon fermentation of lactose, the acidification changes the pH of the agar, causing a color change in the agar to a milky purple, pink color of the colonies.
How to Perform the Semi-Quantitative Urine Streak: First, mix the urine well without creating bubbles. Dip once each for the blood plate or blood side and once again for the MacConkey plate or the MacConkey side of the biplate.
Example of gamma-hemolytic, Coagulase-negative Staphylococci growing on the blood plate. With the 0.001 loop (small), each colony represents 1,000 CFU/mL, therefore, this plate would be quantitated as >100,000 CFU/mL.http://people.upei.ca/jlewis/assets/images/Urine-quan-BA-2_wb.jpg
An example of a urine biplate by Hardy Diagnostics,http://hardydiagnostics.com
An example of a urine biplate by Hardy Diagnostics.http://hardydiagnostics.com
Lactose-fermenting Escherichia coli growing on the MacConkey plate, "pinkening" the agar. This organism is the #1 cause of Urinary Tract Infections overall, and the #1 cause of nosocomial (hospital-acquired) infections.By Microrao JJMMC, Davangere, Karnataka, India - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7633534
Non-lactose-fermenting Hafnia alvei on a MacConkey agar plate.By Unknown - http://phil.cdc.gov ID #6608, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11503395
CASTS:
Casts are unique to the kidney, and are formed i the distal and collecting tubules of the kidney. They consists of a core matrix of Tamm-Horsfall protein, or uromodulin, a glycoprotein secreted by the renal tubular cells lining the thick portion of the ascending loop of Henle, as well as by the distal convoluted tubules. Uromodulin protein forms fibrils, which anchor it to the lumen cells, enmeshing formed elements into its matrix. Eventually, this is flushed out with the urine when it detaches from the tubular epithelial cells.
Casts are cylindrical in shape and appear thicker in the middle. Wide or broad casts are formed in extremely dilated tubules or in a wide collecting duct. Cast formation is enhanced in acidic pH, increased solute concentration, urine stasis, and increased proteins like albumin. A few hyaline or finely granular casts in the urine may be normal. They can form after strenuous exercise as well.
Casts are classified microscopically based on their matrix composition and the formed elements trapped within them:
Homogenous Matrix
Hyaline
uromodulin protein matrix
cylindroid
most commonly observed casts in the urine sediment
low refractive index
transparent, colorless, rounded ends
0-2 are normal in a healthy individual/LPF
increased after strenuous exercise, dehydration, fever, emotional stress
Rule out: renal disease, congestive heart failure
Waxy
waxy appearance
high refractive index
well-defined edges with sharp, blunt or uneven ends and cracks or fissures
colorless, gray or yellow
diffuse, ground-glass appearance in stain
indicate prolonged urine stasis and tubular obstruction
Rule out: advanced stage of other casts associated with chronic renal failure, acute renal disease, acute glomerulonephritis, acute pyelonephritis, nephrotic syndrome, malignant hypertension, real allograft rejection
Cellular Inclusions
RBCs
intact RBCs within matrix
blood and protein +
rarely observed after contact sports
Rule out: acute glomerulonephritis, nephritis
Leukocytes/WBCs
intact WBCs within matrix
Protein +, LE +, Blood +/-. Nitrite +/-
Rule out: infection or inflammation or autoimmune disease
Renal Tubular Epithelial Cells (RTEs)
RTE cells within matrix
protein +, blood +/-
Rule out: Acute tubular necrosis, all types of renal disease
Mixed Cells: mix of cellular types trapped in the matrix
Bacteria
bacteria trapped in a matrix
protein +, LE +, nitrate +/-, blood +/-
bacterial pyelonephritis
Fungal
Fungi trapped within matrix
protein +, LE +, blood +/-
fungal pyelonephritis
Other Types
Granular
Finely Granular: small granules from renal cell metabolic byproducts found throughout the matrix, giving it the appearance of "sandpaper"
strenuous exercise, stress, dehydration, fever
Coarse Granular: large, coarse granules from degenerating cells, trapped cell debris, and metabolic byproducts found in the matrix
found with other pathologic casts in urine sediment
associated with renal calculi (stones) or drug precipitation or dehydration
Pigmented (Colored)
Hemoglobin (pink-red or yellow-brown)
Myoglobin (red-brown)
Bilirubin (yellow-brown)
Size
Broad or Wide
formation in dilated tubules or large collecting ducts
poor prognosis
chronic renal diseases
Narrow
Kidney Stones:
Kidney stone forms in the urinary tract (kidney, renal pelvis, or bladder)
>0.2 inches can block the ureter, resulting in pain, reduced urine stream, kidney infection, blood in the urine, painful urination, and even vomiting
Genetics and environmental factors play a role
Dehydration, high calcium levels, calcium supplements, vitamin C supplements, gout, hyperparathyroidism, some foods, and some medications can contribute to the formation of kidney stones